Tuned Mass Damper

A Tuned Mass Damper (TMD) is a mechanical device, that you can buy at Flow Engineering, designed to add damping to a structure. Using its expertise, Flow Engineering can provide damper systems to prevent or remove excessive vibrations on your structure. You are welcome to contact us for more information or for your inquiry about a tuned mass damper system.

Working Principle of the Tuned Mass Damper

A Tuned Mass Damper, that you can order at our company, consists of a suspended mass that moves in the same direction as the vibration direction. It is tuned to the oscillation frequency of the vibration using either a spring system or pendulum system. When the structure starts to oscillate, the mass of the TMD mass will resonate with the vibration. A damper component connected between the structure and the TMD mass then turns the kinetic energy of the vibration into thermal energy, which effectively adds damping, and limits the amplitude of the vibrations. The design of an TMD depends on the oscillation frequency, mass of the structure, the direction of the movements (one horizontal direction, two horizontal directions, or vertical), and the available space.

Guarantee

Flow Engineering has more than 20 years of experience in the calculation, designing, manufacturing, and installation of Tuned Mass Damper (TMD) systems. Our TMD systems are applied to bridges, flagpoles, chimneys, distillation columns and other slender structures.

Our TMD systems have proven themselves in practice. We guarantee that the solutions we offer ensures the reduction of unwanted vibrations to an acceptable level, thereby preventing fatigue damage.

Advanced TMD Designs

By cleverly designing a Tuned Mass Damper (TMD) – that you can buy at Flow Engineering – a single device can add sufficient damping for o or more of the structure’s natural frequencies, limiting the number of necessary TMDs. Using our own developed unique TMD design software, we can guarantee correct operation within a specified design range even when using multiple TMDs for a single structure.

Design considerations

For a single mode of vibration, a structure with a Tuned Mass Damper can be modelled as in the following figure.

Here k refers to the spring constant, c the damper constant, and m is the mass. Subscript 1 pertains to the structure and subscript 2 to the TMD. A TMD can significantly reduce the response of a structure, as can be seen from the following graph.

The effects of varying several design parameters are given below.

Mass of Structure

Increasing the mass ratio μ (increasing the damper mass vs the mass of the vibrating structure) will decrease the structural displacement. The normalized structural displacement amplitude can be computed with the formula given by J.P. Den Hartog in “Mechanical Vibrations”:

The normalized structural displacement amplitude is a measure of amplification compared to the displacement of an equivalent static load. So, in other words, a normalized displacement of 20 means the structure will move 20 times compared to a static load of equivalent force. (H(f_0)/H(0)=20)

A structure without TMD can have a normalized structural displacement amplitude up to 250. As can be seen from the figure, Den Hartog’s approach, calculating with ζ1=0ζ1=0, is slightly conservative for steel structures (ζ1=0.2%ζ1=0.2%) at the lower mass ratios.

Damper Frequency

The eigenfrequencies of a structure may not be known to a sufficient level of accuracy at the time that the TMDs are designed. It is then useful to define a range in which the frequency of the eigenmode to be damped is sure to reside. By designing an appropriate Tuned Mass Damper for the entire range, the TMD can be designed and produced without the need for measuring the structure eigenfrequencies.

In the case that the structure has multiple eigenfrequencies relatively near to each other, a TMD with a wide effective frequency range may be used to add damping to several eigenmodes. Reducing the cost of the vibration damping system.

TMD Damping Ratio

The increase in amplitude from mistuned internal damping can be significant. It is because of this effect that we advise changing the internal dampers at set intervals of 15 to 25 years, depending on the damper used.